CN109642286A - Ferrite-group stainless steel hot-roll annealing steel plate and its manufacturing method - Google Patents

Ferrite-group stainless steel hot-roll annealing steel plate and its manufacturing method Download PDF

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CN109642286A
CN109642286A CN201780051736.3A CN201780051736A CN109642286A CN 109642286 A CN109642286 A CN 109642286A CN 201780051736 A CN201780051736 A CN 201780051736A CN 109642286 A CN109642286 A CN 109642286A
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steel plate
content
rolling
ferrite
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CN109642286B (en
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吉野正崇
藤泽光幸
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JFE Steel Corp
JFE Engineering Corp
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NKK Corp
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    • C21D6/004—Heat treatment of ferrous alloys containing Cr and Ni
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    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
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    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
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    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
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    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/26—Methods of annealing
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    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
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Abstract

The present invention provides the ferrite-group stainless steel hot-roll annealing steel plate and its manufacturing method of crackle when there is sufficient corrosion resistance and being able to suppress to be formed for the punch press process of heavy wall flange.A kind of ferrite-group stainless steel hot-roll annealing steel plate, it is characterized in that, with in terms of quality % containing C:0.001~0.020%, Si:0.05~1.00%, Mn:0.05~1.00%, P:0.04% or less, S:0.01% or less, Al:0.001~0.100%, Cr:10.0~24.0%, Ni:0.01~0.60%, Ti:0.10~0.40%, N:0.001~0.020%, surplus be made of Fe and inevitable impurity at being grouped as, critical stress intensity factors KICFor 20MPam1/2More than.

Description

Ferrite-group stainless steel hot-roll annealing steel plate and its manufacturing method
Technical field
The present invention relates to the ferrite-group stainless steel hot-roll annealing steel plate for the excellent processability for being suitably applied flange etc. and Its manufacturing method.
Background technique
In recent years, the reinforcing of legal provisions relevant to the exhaust gas of automobile is being promoted, improving fuel efficiency becomes when business It is anxious.Therefore, it is promoting and is following the exhaust gas that the exhaust gas generated by automobile engine is used as the air inlet of engine to use again again Ring (Exhaust Gas Recirculation, EGR) systematic difference.The exhaust gas generated by engine is for reducing gas It is supplied again after passing through in the cooler for recycled exhaust gas of temperature to engine.When making waste gas circulation, the leakage of exhaust gas in order to prevent, respectively Exhaust system component is connected by flange.Flange applied in such exhaust system component needs to have adequately rigidity. Therefore, the flange of heavy wall (such as 5mm or more is calculated as with plate thickness) can be applied in such exhaust system component.
In the past, the flange of heavy wall used ordinary steel.But pass through for being applied to the high-temp waste gas as egr system For the flange of component, it is desirable that sufficient corrosion resistance.Therefore, for compared with ordinary steel the stainless steel of excellent corrosion resistance, Especially coefficient of thermal expansion is smaller and be difficult to generate the application of the ferrite-group stainless steel of thermal stress and studied, and is strongly required energy (such as 5mm or more is calculated as with plate thickness) ferrite series stainless steel plate enough big applied to the plate thickness of heavy wall flange.
For such market demands, for example, Patent Document 1 discloses a kind of ferrite-group stainless steel hot-rolled steels Plate, wherein in terms of quality %, containing C:0.015% or less, Si:0.01~0.4%, Mn:0.01~0.8%, P:0.04% with Under, S:0.01% or less, Cr:14.0%~less than 18.0%, Ni:0.05~1%, Nb:0.3~0.6%, Ti:0.05% with Under, N:0.020% or less, Al:0.10% or less, B:0.0002~0.0020%, surplus be Fe and inevitable impurity, The content of Nb, C and N meet Nb/ (C+N) >=16, and the charp impact value at 0 DEG C is 10J/cm2More than, plate thickness be 5.0~ 9.0mm。
Existing technical literature
Patent document
Patent document 1: International Publication No. 2014/157576
Summary of the invention
Problem to be solved by the invention
But the present inventor has attempted to be processed into using the ferrite-group stainless steel hot rolled steel plate recorded in patent document 1 The flange shape of heavy wall with flange processing portion, the results showed that, although above-mentioned steel plate has sufficient charp impact value, It is that the especially plate thickness central portion in flange processing portion cracks sometimes, scheduled flange shape cannot be obtained, be not enough to answer Flange for heavy wall.
The purpose of the present invention is to solve the above problem, provides with sufficient corrosion resistance and is able to suppress progress The ferrite-group stainless steel hot-roll annealing steel plate and its manufacturing method of crackle when being configured to the punch press process of heavy wall flange.
The method for solving problem
The present inventor is studied in detail to solve the above-mentioned problems.Itself as a result, it has been found that, be more than the thickness of 5.0mm by plate thickness When wall steel plate is configured to the heavy wall flange with flange processing portion in the case where not cracking, processability utilizes previous one The charp impact value directly used is unable to accurate evaluation, still, using as the limit stress of the toughness evaluation index in slab field Intensity factor (Threshold Stress Intensity Factor) KICIt can accurately be evaluated.It is thought that because are as follows: For sheet metal of the plate thickness less than 5.0mm, the plastic deformation area near punching end face portion when processing is relative to plate thickness It is larger, therefore, it cannot entirely be arranged using the processing in terms of fracture mechanics and shape associated breakoff phenomenon, in contrast, For plate thickness is the thick steel sheet of 5.0mm or more, fully meet the plastic deformation in portion near punching end face when processing Region is relative to plate thickness sufficiently small small-scale yield situation, therefore, can utilize the quantitative target in terms of as fracture mechanics Stress intensity factor pair handled with the associated breakoff phenomenon of defined processing, in particular with its critical value, i.e. critical Stress strength factor KICIt can accurately be evaluated.
For above situation, the generation and limit stress that whether there are cracks when the present inventor is to the flange for being processed into regulation shape Intensity factor KICRelationship carried out probe.Itself as a result, it has been found that, by by critical stress intensity factors KICIt is set as 20MPa·m1/2More than, it can effectively inhibit and be generated when being processed into the heavy wall flange with flange processing portion in flange processing portion Crackle, can be fully practical in the heavy wall flange with flange processing portion.
In addition, it is found that for the ferrite-group stainless steel of proper composition, especially for suitably controlling by three passages Accumulation reduction ratio (=100- (the final plate thickness/final for final three passages in hot finishing process that above multi-pass is constituted The rolling of three passages start before plate thickness) × 100 [%]) and obtained from hot rolled steel plate, by carrying out at a proper temperature Hot rolled plate annealing, critical stress intensity factors KICIt improves.
The present invention is completed based on the above opinion, and purport is as described below.
[1] a kind of ferrite-group stainless steel hot-roll annealing steel plate, which is characterized in that have and contain C in terms of quality %: 0.001~0.020%, Si:0.05~1.00%, Mn:0.05~1.00%, P:0.04% or less, S:0.01% or less, Al: 0.001~0.100%, Cr:10.0~24.0%, Ni:0.01~0.60%, Ti:0.10~0.40%, N:0.001~ 0.020%, surplus be made of Fe and inevitable impurity at being grouped as, critical stress intensity factors KICFor 20MPam1/2 More than.
[2] the ferrite-group stainless steel hot-roll annealing steel plate as described in above-mentioned [1], which is characterized in that as at being grouped as, In terms of quality % also containing selected from Cu:0.01~1.00%, Mo:0.01~2.00%, W:0.01~0.20%, Co:0.01~ One or more of 0.20%.
[3] the ferrite-group stainless steel hot-roll annealing steel plate as described in above-mentioned [1] or [2], which is characterized in that as ingredient Composition, also containing selected from V:0.01~0.20%, Nb:0.01~0.10%, Zr:0.01~0.20%, REM in terms of quality %: 0.001~0.100%, B:0.0002~0.0025%, Mg:0.0005~0.0030%, in Ca:0.0003~0.0030% It is one or more kinds of.
[4] a kind of manufacturing method of ferrite-group stainless steel hot-roll annealing steel plate is any one of above-mentioned [1]~[3] The manufacturing method of the ferrite-group stainless steel hot-roll annealing steel plate, which is characterized in that in the essence for carrying out three passages or more In the hot-rolled process rolled, the temperature range of final three passages of finish rolling is set as 800~1100 DEG C and will be above-mentioned final The accumulation reduction ratio of three passages is set as 25% or more and obtains hot rolled steel plate, to the hot rolled steel plate further 800~ Hot rolled plate annealing is carried out at 1100 DEG C.
Here, critical stress intensity factors KICRefer to stress intensity factor as described below, that is, with fatigue precracking line be roll Right angle orientation processed, stress axis are to roll the mode of parallel direction to cut CT (compact drawing according to ASTM E399 from the wide central portion of plate Stretch, Compact Tension) test film, it is tested according to ASTM E399, thus obtained stress intensity factor.
Invention effect
According to the present invention it is possible to obtain that there is sufficient corrosion resistance and be able to suppress to be formed as heavy wall flange Punch press process when crackle excellent processability ferrite-group stainless steel hot-roll annealing steel plate.
It should be noted that the sufficient corrosion resistance in the present invention refers to, will evaluate using #600 sand paper The steel plate that end face portion is sealed after surface grinding polishing carries out the circulation examination of brine spray specified in the JIS H 8502 of 5 circulations It tests (by brine spray (5 mass %NaCl, 35 DEG C, by spraying 2 hours) → dry (60 DEG C, 4 hours, relative humidity 40%) → profit Wet (50 DEG C, 2 hours, relative humidity >=95%)) it is set as the test of 1 circulation), the face of getting rusty in the evaluation face of steel plate at this time Product rate (=rust area/steel plate gross area × 100 [%]) is 25% or less.
In addition, the excellent processability for being able to suppress crackle when being formed as the punch press process of heavy wall flange refers to, with The mode that fatigue precracking line is rolling right angle orientation, stress axis is rolling parallel direction is cut from the wide central portion of plate according to ASTM The CT test film of E399 is tested, thus obtained critical stress intensity factors K according to ASTM E399ICFor 20MPam1/2 More than.
Specific embodiment
Ferrite-group stainless steel hot-roll annealing steel plate of the invention have in terms of quality % containing C:0.001~0.020%, Si:0.05~1.00%, Mn:0.05~1.00%, P:0.04% or less, S:0.01% or less, Al:0.001~0.100%, Cr:10.0~24.0%, Ni:0.01~0.60%, Ti:0.10~0.40%, N:0.001~0.020%, surplus are by Fe and not Evitable impurity constitute at being grouped as, critical stress intensity factors KICFor 20MPam1/2More than.
Critical stress intensity factors KICRefer to, with fatigue precracking line be rolling right angle orientation, stress axis is to roll parallel side To mode cut the CT test film according to ASTM E399 from the wide central portion of plate, tested according to ASTM E399, thus The stress intensity factor arrived.
Hereinafter, being described in detail to the present invention.
The present inventor is that the various ferrite series stainless steel plates of 5.0mm are configured to have by 30mm φ's for using plate thickness It is cracked when flange hole portion is from the flange in the flange processing portion that the surface of steel plate of slab state (punching state) promotes 10mm Reason is studied in detail.Itself as a result, it has been found that, in the above-mentioned steel plate for producing crackle, punching end face plate thickness central portion The small cracking nearby generated significantly develops in flange processing, therefore, cracks.
The significant development of the small cracking and the relationship of material property is studied in detail in the present inventor.Its result hair Now there is following tendency: the critical stress intensity factors K of steel plateICSmaller, then the development of small cracking is more easy to happen.Therefore, It has attempted to be configured to the flange using various ferrite-group stainless steel hot-roll annealing steel plates (plate thickness 5.0mm), as a result, it has been found that, because micro- Crackle caused by the development of small cracking is for the critical stress intensity factors K that is obtained using defined measuring methodICIt is lower than 20MPa·m1/2Steel plate for be particularly easy to generate.
In addition, the present inventor is in order to produce the critical stress intensity factors of the steel plate of crackle when being clearly configured to the flange KICSmall reason has carried out probe to the crackle portion of above-mentioned steel plate.Itself as a result, it has been found that, in the steel plate for producing crackle, Grain boundaries of the cracking generated near the plate thickness central portion of punching end face near plate thickness central portion significantly develop.
Also, (electronics is carried on the back using SEM (scanning electron microscope, Scanning Electron Microscopy)/EBSD Scattering and diffracting, Electron Backscatter Diffraction) method to the tissue of above-mentioned steel plate carried out investigate and solve Analysis, as a result, it has been found that, although the crystal grain at the position significantly developed that is cracked is crystal grain independent, still, formed and adjacent crystalline substance Grain is with roughly the same crystal orientation, so-called cluster (the crystal grain group with similar crystal orientation).In general, crystal grain and phase Adjacent crystal grain has different crystal orientations, is cracked when developing on crystal boundary and is orientated obstruction of the different crystal boundaries as cracking development It functions.But the crystal orientation of crystal grain adjacent in cluster is substantially equivalent, therefore, by each intercrystalline in cluster Crystal boundary bring inhibits the effect of cracking development small, for being formed with the steel plate of cluster, critical stress intensity factors KICIt reduces, is configured to produce crackle when the flange.
Therefore, the present inventor, which is directed to, makes critical stress intensity factors for ferrite-group stainless steel hot-roll annealing steel plate KICThe method of raising has made intensive studies.Itself as a result, it has been found that, for the ferrite-group stainless steel of proper composition, especially for Suitable control is carried out to make the temperature range of final three passages for the hot-rolled process for carrying out the finish rolling being made of multi-pass The accumulation reduction ratio of 800~1100 DEG C and final three passages ((open=100- by the rolling of final plate thickness/final three passages Plate thickness before beginning) × 100 [%]) it is hot rolled steel plate obtained from 25% or more, hot rolled plate is carried out at 800~1100 DEG C to move back Fire, cluster is effectively destroyed as a result, has obtained 20MPam1/2Above critical stress intensity factors KIC。
It should be noted that the plate thickness of ferrite-group stainless steel hot-roll annealing steel plate of the invention is not particularly limited, the phase The plate thickness that can be applied to the flange of heavy wall is hoped, it is therefore preferable that being 5.0mm or more, more preferably 7.0mm or more.In addition, above-mentioned Plate thickness is not particularly limited, and preferably 15.0mm is hereinafter, more preferably 10.0mm or less.
The reasons why destruction that can promote cluster by the above method, is illustrated below.
The plate thickness central portion of steel billet before the hot rolling of ferrite-group stainless steel, coarse and stretching, extension cluster (have similar The crystal grain group of crystal orientation) being connected along casting direction is distributed.On the other hand, in the case where being rolled to steel plate, steel plate from Surface section starts anamorphic stretching.Therefore, in the case that reduction ratio is small, the deflection of plate thickness central portion is small, several in plate thickness central portion It is imported into without rolling strain.
Therefore, it in the hot rolling carried out using the prior art, is not filled in the stretching, extension crystal grain of the plate thickness central portion of steel plate Point ground imports rolling strain, and the recrystallization site in hot rolled plate annealing later is insufficient, although when hot rolled plate is annealed in plate thickness Centre nearby recrystallizes, and still, cluster is not divided and is easy residual, is unable to get the required 20MPam of the present invention1/2 Above critical stress intensity factors KIC。
In addition, dynamic recrystallization occurs for ferrite-group stainless steel (referred to as in machining deformation again in hot rolling Crystallization), processing strain caused by having because of rolling is easy to happen the tendency of recovery.Therefore, in the heat carried out using the prior art In rolling, the processing strain imported by rolling occurs excessively to restore effectively maintain processing strain to hot rolling.Its As a result, recrystallization site is insufficient, cluster is not destroyed effectively in the annealing of next process hot rolled plate, is unable to get rule Fixed critical stress intensity factors KIC。
Therefore, the present inventor is for effectively and fully processing the entire of strain importing steel plate for rolling in hot-rolled process The method of thickness has made intensive studies.Itself as a result, it has been found that, by final three passage management of hot finishing in temperature model appropriate It encloses, and is rolled on this basis with big accumulation reduction ratio, thereby, it is possible to obtain inhibiting to roll the recovery for processing strain While, rolling processing strain sufficiently and is efficiently directed into the central portion to plate thickness to make to anneal in next process hot rolled plate In become the rolling processing strain fully remaining hot rolled plate tissue in recrystallization site, rolled into a ball in the annealing of next process hot rolled plate Cluster is effectively destroyed.
Suitable control is carried out specifically, proposing to make by the final of the hot finishing process that more than three passages constitutes The temperature range of three passages be 800~1100 DEG C and final three passages accumulation reduction ratio (=100- (final plate thickness/ The rolling of final three passages start before plate thickness) × 100 [%]) and be 25% or more and carry out hot rolling.
In addition, the felicity condition that the present inventor anneals for next process hot rolled plate also has made intensive studies.Hot rolled plate Annealing is to make the process of the worked structure recrystallization formed by hot rolling.The temperature that therefore, it is necessary to adequately recrystallize in generation Under anneal.But it when carrying out hot rolled plate annealing at a high temperature of excessively, although recrystallizing, recrystallizes The significant coarsening of crystal grain.The significant coarse recrystal grain is independent single crystal grain, and still, crystal boundary length significantly becomes It is long, it is therefore, and same in the presence of cluster, inhibit the effect of cracking development to reduce by being orientated different crystal boundary brings, can not obtain To defined critical stress intensity factors KIC。
Therefore, the present inventor investigates the partial size of recrystal grain and the relationship of annealing temperature in detail.It is tied Fruit discovery, by the way that hot-roll annealing temperature is suppressed to 1100 DEG C hereinafter, being able to suppress critical stress intensity factors KICSignificant drop The generation of the coarse recrystal grain of low degree.
Then, ferrite-group stainless steel hot-roll annealing steel plate of the invention is illustrated at being grouped as.
Hereinafter, the % of expression composition composition refers to quality % as long as no special declaration.
C:0.001~0.020%
For C containing when having more than 0.020%, the reduction of processability and the corrosion resistance reduction of weld part become significant.From corrosion resistant From the viewpoint of corrosion and processability, the C content the few the more preferred, still, in order to make C content less than 0.001%, when refining is spent Between, in manufacture not preferably.Therefore, C content is set as 0.001~0.020% range.C content is preferably 0.003% or more, More preferably 0.004% or more.In addition, C content is preferably 0.015% hereinafter, more preferably 0.012% or less.
Si:0.05~1.00%
Si has the effect of being enriched in the oxide film thereon formed when welding and improves the corrosion resistance of weld part, and It as deoxidant element is also useful element in steel making working procedure.These effects are available by the Si containing 0.05% or more, The more more then effects of content are bigger.But when containing having more than 1.00% Si, rolling loads respectively occur in hot-rolled process Increase and significant oxide skin generation, in annealing operation occur because steel plate surface layer formation Si enriched layer caused by pickling Property reduction, induce the increase of surface defect, the raising of manufacturing cost, thus not preferably.Therefore, Si content be set as 0.05~ 1.00%.Si content is preferably 0.10% or more.In addition, Si content is preferably 0.60% hereinafter, more preferably 0.40% or less.
Mn:0.05~1.00%
Mn has the effect of improving the intensity of steel, in addition, also having the function of as deoxidier.The effect in order to obtain, Need the Mn containing 0.05% or more.But Mn content, when being more than 1.00%, the generation for becoming the MnS of the starting point of corrosion is promoted Into corrosion resistance reduces.Therefore, Mn content is set as 0.05~1.00%.Mn content is preferably 0.10% or more.In addition, Mn Content is preferably 0.60% hereinafter, more preferably 0.30% or less.
P:0.04% or less
P is the element inevitably contained in steel, but is to corrosion resistance and the harmful element of processability, therefore It is preferred that being reduced as far as.When especially P content is more than 0.04%, processability is significantly reduced due to solution strengthening.Therefore, P contains Amount is set as 0.04% or less.It is preferred that P content is 0.03% or less.
S:0.01% or less
Same as P, S is also the element inevitably contained in steel, but is harmful to corrosion resistance and processability Element, therefore be preferably reduced as far as.When especially S content is more than 0.01%, corrosion resistance is significantly reduced.Therefore, S contains Amount is set as 0.01% or less.It is preferred that S content is 0.008% or less.More preferable S content is 0.003% or less.
Al:0.001~0.100%
Al is effective deoxidier.In addition, the affinity of Al and nitrogen ratio Cr is strong, therefore, when nitrogen invades weld part, make nitrogen with Al nitride rather than the form of Cr nitride are precipitated, and have the effect of inhibiting to be sensitized.These effects by containing 0.001% with On Al and obtain.But when containing having more than 0.100% Al, penetration when welding is reduced and weld job reduces, because This is not preferred.Therefore, Al content is set as 0.001~0.100% range.Al content is preferably 0.005% or more, more preferably It is 0.010% or more.In addition, Al content is preferably 0.060% hereinafter, more preferably 0.040% or less.
Cr:10.0~24.0%
In order to ensure the corrosion resistance of stainless steel, Cr is most important element.When its content is less than 10.0%, in automobile waste Sufficient corrosion resistance is unable to get in gas atmosphere.When on the other hand, containing 24.0% Cr is had more than, because of the life of σ (Sigma) phase At and toughness significantly reduces, in the present invention, cannot obtain as defined in critical stress intensity factors KIC.Therefore, Cr content is set For 10.0~24.0% range.Cr content is preferably 14.0% or more, and more preferably 16.0% or more, further preferably 17.0% or more.In addition, Cr content is preferably 21.5% hereinafter, more preferably 19.5% hereinafter, further preferably 18.5% Below.
Ni:0.01~0.60%
Ni is the element for improving the corrosion resistance of stainless steel, is that activity is occurring in the case where not forming passive state envelope Inhibit the element of the progress of corrosion under the corrosive environment of dissolution.In addition, Ni is strong austenite forming element, has and inhibit welding Ferrite in portion generates, inhibits the effect of sensitization caused by the precipitation because of Cr carbonitride.The effect is by containing 0.01% Above Ni and obtain, the more more then effects of the content of Ni are higher.But Ni content, when being more than 0.60%, not only processability drops It is low, and it is easy to happen stress corrosion cracking.In addition, Ni is expensive element, therefore, the increase of Ni content causes to manufacture The increase of cost, therefore not preferably.Therefore, Ni content is set as 0.01~0.60%.Ni content is preferably 0.10% or more.Separately Outside, Ni content is preferably 0.50% hereinafter, more preferably 0.40% or less.
Ti:0.10~0.40%
Ti is extremely important element in the present invention.Ti, which has, preferentially to be combined to inhibit Cr carbonitride with C and N It is precipitated, reduces recrystallization temperature and inhibit the drop for being sensitized caused corrosion resistance as caused by the precipitation of Cr carbonitride Low effect.These effects in order to obtain need the Ti containing 0.10% or more.But Ti content is when being more than 0.40%, solid solution Ti amount is excessively increased, and therefore, recrystallization temperature increases instead, cannot apply technology of the invention.In addition, containing having more than 0.40% Ti when, coarse Ti carbonitride is generated in casting process, causes surface defect, therefore is manufactured also not preferably.Therefore, Ti content is set as 0.10~0.40%.Ti content is preferably 0.15% or more, and more preferably 0.20% or more.In addition, Ti contains Amount preferably 0.35% is hereinafter, more preferably 0.30% or less.It should be noted that being examined from the viewpoint of corrosion resistance at welded part Consider, be preferably set to meet formula: (it should be noted that in the formula, Ti, C, N are the content (matter of each element to Ti/ (C+N) >=8 Measure %)) Ti content.
N:0.001~0.020%
When N content is more than 0.020%, the reduction of the corrosion resistance of the reduction and weld part of processability becomes significant.From resistance to From the perspective of corrosivity, the N content the low the more preferred, still, in order to which N content is reduced to less than 0.001%, needs for a long time Refining, lead to the raising of manufacturing cost and the reduction of productivity, thus not preferably.Therefore, N content be set as 0.001~ 0.020% range.N content is preferably 0.005% or more, and more preferably 0.007% or more.In addition, N content is preferably 0.015% hereinafter, more preferably 0.012% or less.
The present invention be a kind of ferrite-group stainless steel, which is characterized in that containing above-mentioned neccessary composition, surplus by Fe with can not The impurity avoided is constituted.Furthermore, it is possible to as needed containing selected from one or both of Cu, Mo, W and Co in following ranges Above or/further containing one or more of selected from V, Nb, Zr, REM, B, Mg and Ca.
Cu:0.01~1.00%
Cu for making in aqueous solution or being attached with weakly acidic water droplet in the case where base material and weld part corrosion resistance Raising is particularly effective element.For the effect by obtaining containing 0.01% or more, the more more then said effect of Cu content are higher. But when containing having more than 1.00% Cu, hot-workability reduces and induces surface defect sometimes.In addition, de- after annealing sometimes Oxide skin also becomes difficult.When therefore, containing Cu, Cu content is preferably set to 0.01~1.00% range.Cu content is more excellent It is selected as 0.10% or more, further preferably 0.30% or more.In addition, Cu content is more preferably 0.60% hereinafter, further excellent It is selected as 0.45% or less.
Mo:0.01~2.00%
Mo is the element for significantly improving the corrosion resistance of stainless steel.The effect is obtained by containing 0.01% or more, Content is more, and said effect more improves.But Mo content, when being more than 2.00%, rolling load when hot rolling increases and makes sometimes The property made reduces, or the excessive raising of armor plate strength occurs.In addition, Mo is expensive element, therefore, it is a large amount of contain so that Manufacturing cost increases.When therefore, containing Mo, Mo content is preferably set to 0.01~2.00%.Mo content is more preferably 0.10% More than, further preferably 0.30% or more.In addition, Mo content is more preferably 1.40% hereinafter, further preferably 0.90% Below.
W:0.01~0.20%
Same as Mo, W has the effect of improving corrosion resistance.The effect is obtained and the W containing 0.01% or more. But when containing having more than 0.20% W, intensity is increased sometimes, because the increase etc. of rolling loads causes manufacturing to reduce.Therefore, When containing W, W content is preferably set to 0.01~0.20% range.W content is more preferably 0.05% or more.In addition, W content More preferably 0.15% or less.
Co:0.01~0.20%
Co is the element for improving toughness.The effect is obtained and the Co containing 0.01% or more.On the other hand, Co contains When amount is more than 0.20%, processability is reduced sometimes.When therefore, containing Co, Co content is preferably set to 0.01~0.20% model It encloses.Co content is more preferably 0.10% or less.
V:0.01~0.20%
V and C, N form carbonitride, inhibit sensitization when welding and improve the corrosion resistance of weld part.The effect passes through Keep 0.01% or more V content available.On the other hand, when V content is more than 0.20%, processability and toughness significantly drop sometimes It is low.Therefore, V content is preferably set to 0.01~0.20%.V content is more preferably 0.03% or more.In addition, V content is more preferable For 0.10% hereinafter, being even more preferably 0.05% or less.
Nb:0.01~0.10%
Nb has the effect of miniaturizeing crystal grain and improves the toughness of steel plate and being solid-solution in parent phase.These Effect is available by the Nb containing 0.01% or more.On the other hand, Nb, which also has, makes the raised effect of recrystallization temperature, Nb It is excessively high temperature in order to which the annealing temperature that adequately recrystallization is required occurs in hot rolled plate is annealed when content is more than 0.10% The significant coarsening that crystallization particle diameter is up to the recrystal grain of 300 μm or more degree occurs in annealing, cannot obtain sometimes for degree To defined critical stress intensity factors KIC.When therefore, containing Nb, Nb content is preferably set to 0.01~0.10% range. Nb content is more preferably 0.02% or more.In addition, Nb content is more preferably 0.05% or less.
Zr:0.01~0.20%
Zr has the effect of inhibiting sensitization in conjunction with C and N.The effect is obtained and the Zr containing 0.01% or more. When on the other hand, containing 0.20% Zr is had more than, processability is significantly reduced sometimes.When therefore, containing Zr, Zr content is preferably set For 0.01~0.20% range.Zr content is more preferably 0.02% or more.In addition, Zr content be more preferably 0.10% hereinafter, It is even more preferably 0.05% or less.
REM:0.001~0.100%
REM (Rare Earth Metals: rare earth metal) has the effect of making inoxidizability to improve, and inhibits weld part Oxide film thereon (welding tempering colour) forms and inhibits the formation close to the Cr-depleted region domain of the lower section of oxide film thereon.The effect is by containing There is 0.001% or more REM available.When on the other hand, containing 0.100% REM is had more than, when making cold rolled annealed sometimes The manufacturings such as pickling reduce.When therefore, containing REM, REM content is preferably set to 0.001~0.100% range.REM contains Amount more preferably 0.010% or more.In addition, REM content is more preferably 0.050% or less.
B:0.0002~0.0025%
In order to improve the resistance to secondary processing brittleness after forming, B is effective element.The effect is by setting the content of B It is available for 0.0002% or more.When on the other hand, containing 0.0025% B is had more than, processability and toughness are reduced sometimes.Cause This, when containing B, B content is preferably set to 0.0002~0.0025% range.B content is more preferably 0.0003% or more.Separately Outside, B content is more preferably 0.0006% or less.
Mg:0.0005~0.0030%
Mg is effective element for improving the equiaxial crystal ratio of steel billet, improving processability, toughness.In addition, in picture In the steel containing Ti of the invention such, when Ti carbonitride coarsening, toughness is reduced, and still, Mg, which also has, inhibits Ti carbon nitrogen The coarsening effect of compound.These effects are available by the Mg containing 0.0005% or more.On the other hand, Mg content is super When 0.0030%, deteriorate the surface texture of steel.When therefore, containing Mg, Mg content is preferably set to 0.0005~ 0.0030% range.Mg content is more preferably 0.0010% or more.In addition, Mg content is more preferably 0.0020% or less.
Ca:0.0003~0.0030%
For the blocking of Ca nozzle caused by the partial crystallization for the Ti system field trash being easy to produce when preventing continuously casting It is effective ingredient.The effect is available by the Ca containing 0.0003% or more.But containing the Ca for having more than 0.0030% When, corrosion resistance reduces due to the generation of CaS sometimes.When therefore, containing Ca, Ca content is preferably set to 0.0003~ 0.0030% range.Ca content is more preferably 0.0005% or more.In addition, Ca content be more preferably 0.0015% hereinafter, into One step is preferably 0.0010% or less.
Critical stress intensity factors KIC: 20MPam1/2More than
Ferrite-group stainless steel hot-roll annealing steel plate of the invention is by making critical stress intensity factors KICFor 20MPa m1/2More than, it is able to suppress crackle when being formed as the punch press process of heavy wall flange.Critical stress intensity factors KICPreferably 25MPa·m1/2More than, further preferably 30MPam1/2More than.It should be noted that the flange of heavy wall does not limit especially It is fixed, such as the flange that plate thickness is 5.0mm or more can be enumerated.As above-mentioned flange, such as preferred plate thickness is 5.0~15.0mm's Flange, more preferable plate thickness are the flange of 5.0~10.0mm.
Then, the manufacturing method of ferrite-group stainless steel hot-roll annealing steel plate of the invention is illustrated.It needs to illustrate , in the following description, as long as no special declaration, temperature is set as the utilization surface temperature of steel billet, hot rolled steel plate etc. The surface temperature of the measurements such as meter.
Ferrite-group stainless steel hot-roll annealing steel plate of the invention can obtain as follows: using with mentioned component composition Steel billet, in the hot rolling being made of finish rolling more than roughing and three passages, by the temperature of the rolling of final three passages of finish rolling Degree range is set as 800~1100 DEG C and the accumulation reduction ratio of final three passages is set as 25% or more and obtains heat Rolled steel plate further carries out hot rolled plate annealing to the hot rolled steel plate at 800~1100 DEG C, thus obtains ferrite of the invention It is stainless steel hot-rolling annealed sheet steel.
Firstly, will be made of mentioned component the molten steel that constitutes using method well known to converter, electric furnace, vacuum fusion furnace etc. into Steel former material (steel billet) is made using continuous metal cast process or ingot casting-cogging method in row melting.
The steel billet is heated 1~24 hour at 1100~1250 DEG C or it is after casting 1100 without heating ground The stage of~1250 DEG C of temperature is for hot rolling.In the present invention, about roughing, the content not to be particularly limited to, still, In the case where effectively destroying cast sturcture before hot finishing, in order to make after hot finishing in the miniaturization of crystal grain preferentially play Effect, is preferably set as 65% or more for the accumulation reduction ratio in roughing.Then, regulation plate thickness is rolling to by hot finishing, it will The temperature range of the rolling of final three passages of finish rolling be set as 800~1100 DEG C, will accumulation reduction ratio be set as 25% with Above carry out.
The rolling temperature range of final three passages of hot finishing: 800~1100 DEG C
The accumulation reduction ratio of final three passages of hot finishing: 25% or more
Although coarse cast sturcture is destroyed in the roughing before finish rolling, the crystal grain in the tissue is significantly coarse.For Critical stress intensity factors K as defined in being obtained after hot rolled plate annealingIC, need by suitably control hot finishing final three The temperature of the rolling of a passage inhibits the excessive recovery in rolling with accumulation reduction ratio and especially has to plate thickness central portion Effect ground assigns rolling strain.
As next process hot rolled plate annealing in, in order to obtain as defined in metal structure and import sufficient recrystallization Site, for this reason, it may be necessary to which the rolling temperature of final three passages of hot finishing is set as 800~1100 DEG C of range and is incited somebody to action Accumulation the reduction ratio (=100- (rolling of final plate thickness/final three passages start before plate thickness) × 100 of final three passages [%]) it is set as 25% or more, it is eliminated to prevent from being strained by the rolling that final three passages assign because of recovery, and to plate Thick center effectively assigns rolling strain.
When the accumulation reduction ratio of final three passages of hot finishing is less than 25%, plate thickness center is not assigned effectively and being rolled System strain, therefore, the cluster residual in the annealing of next process hot rolled plate cannot obtain defined critical stress intensity factors KIC。 Therefore, the accumulation reduction ratio of final three passages is set as 25% or more.It is preferred that accumulation reduction ratio is 30% or more.Further It is preferred that accumulation reduction ratio is 35% or more.It should be noted that the upper limit of accumulation reduction ratio is not particularly limited, but press accumulation When lower rate excessively increases, rolling load is increased sometimes and manufacturing reduces, and generates rough surface after rolling, it is therefore preferable that It is set as 60% or less.
When the rolling temperature of final three passages of hot finishing is set to be lower than 800 DEG C, the reduction of adjoint steel billet temperature, Rolling loads significantly increase, therefore manufacture not preferably.In addition, sometimes due to rolling under low temperature and generate the table of surface of steel plate Face is coarse to cause surface quality to reduce.On the other hand, it when the rolling temperature of final three passages is more than 1100 DEG C, is assigned because of rolling The strain given restores, and the recrystallization site after next process hot rolled plate annealing is insufficient, therefore, the cluster after hot rolled plate annealing Residual cannot obtain defined critical stress intensity factors KIC.Therefore, the rolling temperature of final three passages be set as 800~ 1100 DEG C of range.It is preferred that the rolling temperature of final three passages is set as 800~1050 DEG C of range.More preferably final three The rolling temperature of passage is set as 850~1000 DEG C of range.
It should be noted that applying excessive roll in the specific passage in final three passages of hot finishing in order to prevent The rolling temperature range of first passage in final three passages is preferably set as 950~1100 DEG C, will be then somebody's turn to do by load processed The rolling temperature range for second passage that first passage carries out is set as 925~1075 DEG C, will then second passage The rolling temperature range of the third passage of progress is set as 875~1050 DEG C.
In addition, the manufacturing method of ferrite-group stainless steel hot-roll annealing steel plate of the invention it is characterized in that, by three Temperature range is controlled in final three passages of the hot finishing more than a passage constituted, and applies big pressure on this basis. When carrying out applying the rolling of big pressure in more than four final passages, even identical accumulation reduction ratio, reduction ratio Also it is scattered in each passage, it is therefore, insufficient to the imparting strain of plate thickness center, and the accumulation shipping time between each passage increases, Therefore, the recovery during transporting between each passage has been encouraged, the effect for assigning strain reduces.In addition, by the rolling temperature of finish rolling When control with accumulation reduction ratio is set as two final passages or less, exist to carry out accumulation pressure in two passages Big pressure that rate is 25% or more and rolling load significantly increases the case where reducing to manufacturing, therefore it is not preferred.Therefore, In the manufacturing method of ferrite-group stainless steel hot rolled steel plate of the invention, to the rolling temperature of three final passages of finish rolling It is controlled with accumulation reduction ratio.
It should be noted that in the manufacturing method of ferrite-group stainless steel hot rolled steel plate of the invention, it is important that control The rolling temperature and accumulation reduction ratio for heating three final passages of finish rolling, when being the finish rolling of three passages or more, Ke Yijin The finish rolling of any passage of row still when maximum road number is more than 15 passages, is held because of the increase with the frequency of exposure of Rolling roller The reduction that steel billet temperature easily occurs, exists to maintain steel billet temperature within the scope of predetermined temperature and needs to add from external Heat etc. cause manufacturing reduction or manufacturing cost increase the case where, therefore, maximum road number is preferably set to 15 passages Below.More preferably up to road number is 10 passages or less.
After hot finishing, the cooling of steel plate is carried out, then carry out steel plate batches processing, and hot rolled strip is made.In the present invention In, coiling temperature is not particularly limited, by coiling temperature be set greater than 450 DEG C~lower than 500 DEG C when, occur sometimes because of 475 Embrittlement caused by DEG C embrittlement.Therefore, coiling temperature is preferably set to 450 DEG C or less or 500 DEG C or more.
Hot-roll annealing temperature: 800~1100 DEG C
In the present invention, hot rolled plate annealing is carried out after above-mentioned hot-rolled process.In hot rolled plate annealing, make in hot rolling The rolling worked structure recrystallization formed in process.In the present invention, rolling strain is effectively assigned in hot-rolled process, is made again Crystalline sites increase, and thus promote the destruction of the cluster in hot rolled plate annealing.The effect in order to obtain, needs 800~1100 Hot rolled plate annealing is carried out in the range of DEG C.When annealing temperature is lower than 800 DEG C, recrystallization is become inadequate, and cannot be obtained defined Critical stress intensity factors KIC.On the other hand, when annealing temperature is more than 1100 DEG C, its crystallization particle diameter maximum occurs for recrystal grain For the significant coarsening of 300 μm or more degree, defined critical stress intensity factors K cannot be obtainedIC.Therefore, hot rolled plate is annealed Temperature is set as 800~1100 DEG C of range.Hot rolled steel plate after having carried out hot rolled plate annealing is formed with mentioned component, tool There is 20MPam1/2Above critical stress intensity factors KIC.It is preferred that the range that hot-roll annealing temperature is 800~1050 DEG C.Into The range that the preferred hot-roll annealing temperature of one step is 850~1000 DEG C.It should be noted that hot rolled plate annealing retention time and Method is not particularly limited, and is implemented using any one of box annealing (batch anneal), continuous annealing.
Obtained hot-roll annealing steel plate can according to need and carry out the processing of deoxygenated skin using shot-peening, pickling.This Outside, in order to improve surface texture, it is possible to implement grinding, grinding etc..In addition, can after hot-roll annealing steel plate provided by the present invention To carry out cold rolling and cold-reduced sheet annealing.
Embodiment
Hereinafter, by embodiment, the present invention is described in detail.
Stainless molten steel with chemical composition shown in table 1 is blown using 150 tons of capacity of converter and strong mixing vacuum The refining of oxygen carbonization treatment (SS-VOD) carries out melting, and the steel billet of width 1000mm, thickness 200mm are made up of continuously casting. Other than No.31, after which is heated 1 hour at 1200 DEG C, as hot rolling, the reversible using three sections of bases is carried out Roughing the steel plate of about 40mm is made, then documented by the table 2 under the conditions of carry out the final of the finish rolling being made of seven passages Three passages (the 5th passage, the 6th passage, the 7th passage), are made hot rolled steel plate.No.31 is by the steel billet 1300 For hot rolling after being heated 1 hour at DEG C.For obtained hot rolled steel plate, case is utilized under the conditions of documented by the identical table 2 Formula annealing carries out hot rolled plate annealing, obtains hot-roll annealing plate.
For obtained hot-roll annealing steel plate, following evaluation is carried out.
(1) critical stress intensity factors KICEvaluation
It is cut in such a way that fatigue precracking line is rolling right angle orientation, stress axis is rolling parallel direction from the wide central portion of plate CT test film according to ASTM E399.For the test film, critical stress intensity factors K is found out according to ASTM E399IC.It will face Boundary's stress strength factor KICFor 20MPam1/2It is set as qualified above, 20MPam will be less than1/2It is set as unqualified.
(2) evaluation of corrosion resistance
The test film of 60 × 100mm is cut from hot-roll annealing steel plate, makes the surface that will be evaluated using #600 sand paper The test film that end face portion is sealed after grinding and polishing, for brine spray cyclic test specified in JIS H 8502.Salt water spray In mist cyclic test, by brine spray (5 mass %NaCl, 35 DEG C, by spraying 2 hours) → dry (60 DEG C, 4 hours, relative humidity 40%) → wetting (50 DEG C, 2 hours, relative humidity >=95%) is set as 1 circulation, carries out 5 circulations.It is recycled to implementing 5 Brine spray cyclic test after test film evaluation face carry out photograph taking, pass through the evaluation of image analysis measurement test piece The rust area in face goes out scale rate ((rust area/test film in test film according to the ratio calculation with the test film gross area The gross area) × 100 [%]).It is 10% or less to be set as particularly excellent corrosion resistance and qualification (◎), will be greater than by scale rate 10% and 25% or less it is set as qualified (zero), will be greater than 25% and be set as unqualified (×).
Test result and hot rolling and hot rolled plate annealing conditions are shown in Table 2 together.
Composition of steel, hot-rolled condition and hot rolled plate annealing conditions meet in No.1~26 of the scope of the present invention, pass through regulation Hot rolling and hot rolled plate annealing destroy cluster effectively, as a result obtained defined critical stress intensity factors KIC.In addition, The corrosion resistance of obtained hot-roll annealing plate is evaluated, is as a result confirmed: scale rate 25%, it may have sufficiently Corrosion resistance.
Especially in No.5~7 and No.10 for having used steel E, F, G, J containing Mo and the steel H containing Cu is used In the No.8 of I and 9, the more excellent corrosion resistance that scale rate is 10% or less (◎) has been obtained.
In the No.27 that the rolling temperature of final three passages is more than the scope of the present invention, although with defined accumulation pressure Lower rate is rolled, but rolling temperature is excessive temperature, therefore, the recovery of processing strain occurs and recrystallizes site and does not fill Point, therefore, cluster still remains after hot rolled plate annealing, does not obtain defined critical stress intensity factors KIC。
In No.28 of the accumulation reduction ratio of final three passages lower than the scope of the present invention, imported to plate thickness central portion Rolling processing strain is insufficient, therefore, after hot rolled plate annealing, still remains in plate thickness central portion cluster, is not as a result advised Fixed critical stress intensity factors KIC。
In the No.29 that hot-roll annealing temperature is more than the scope of the present invention, recrystal grain generated occurs significant As a result coarsening does not obtain defined critical stress intensity factors KIC。
In No.30 of the hot-roll annealing temperature lower than the scope of the present invention, recrystallization is insufficient, and therefore, cluster does not have It is destroyed and remains, as a result do not obtain defined critical stress intensity factors KIC。
No.31 is to roll after heating steel billet 1 hour at 1300 DEG C for hot rolling, final three passages for making hot finishing Example of the temperature range processed more than 1100 DEG C.In No.31, excessive add occurs in the rolling for implementing final three passages The recovery of work strain and to recrystallize site insufficient, therefore, cluster still remains after hot rolled plate annealing, do not obtain as defined in face Boundary's stress strength factor KIC。
In the No.32 that the rolling temperature range of final three passages is below the scope of the present invention in three passages, Rolling loads significantly increase, and implementing load when the rolling of final third passage has been more than device allowed band, it is thus impossible to complete At rolling, defined evaluation not can be carried out.
In having used the No.33 that Ti content is more than the steel V of the scope of the present invention, temperature is recrystallized because containing excessive Ti It spends and increases, there is no adequately recrystallizing and cluster residual carrying out defined hot rolled plate annealing, as a result do not obtain Defined critical stress intensity factors KIC.On the other hand, used Ti content lower than the scope of the present invention steel W No.34 In, hot rolled plate is sensitized due to Cr carbonitride is largely precipitated when annealing, and cannot obtain defined corrosion resistance.In addition, It has used Ti content lower than the scope of the present invention and Nb content is more than Nb content mistake in the No.35 of steel Z of the scope of the present invention Amount, therefore, hot rolled plate annealing in order to obtain sufficient recrystallized structure and need excessive high annealing, the result is that occur Significant toughness caused by the significant coarsening of the recrystal grain generated by hot rolled plate annealing reduces, therefore, not To defined critical stress intensity factors KIC.In addition, Ti content is insufficient, therefore, in hot rolled plate annealing, Cr carbonitride is big Amount, which is precipitated, to be caused to be sensitized, and can not obtain defined corrosion resistance.
Industrial availability
The ferrite-group stainless steel hot-roll annealing steel plate obtained in the present invention is particularly suitable for demanding processing The purposes of property and corrosion resistance, such as the flange with flange processing portion.

Claims (4)

1. a kind of ferrite-group stainless steel hot-roll annealing steel plate, which is characterized in that
With in terms of quality % contain C:0.001~0.020%, Si:0.05~1.00%, Mn:0.05~1.00%, P: 0.04% or less, S:0.01% or less, Al:0.001~0.100%, Cr:10.0~24.0%, Ni:0.01~0.60%, Ti: 0.10~0.40%, N:0.001~0.020%, surplus be made of Fe and inevitable impurity at being grouped as,
Critical stress intensity factors KICFor 20MPam1/2More than.
2. ferrite-group stainless steel hot-roll annealing steel plate as described in claim 1, which is characterized in that as at being grouped as, with Quality % meter also containing selected from Cu:0.01~1.00%, Mo:0.01~2.00%, W:0.01~0.20%, Co:0.01~ One or more of 0.20%.
3. ferrite-group stainless steel hot-roll annealing steel plate as claimed in claim 1 or 2, which is characterized in that as at being grouped as, Also containing selected from V:0.01~0.20%, Nb:0.01~0.10%, Zr:0.01~0.20%, REM:0.001 in terms of quality % ~0.100%, one of B:0.0002~0.0025%, Mg:0.0005~0.0030%, Ca:0.0003~0.0030% Or it is two or more.
4. a kind of manufacturing method of ferrite-group stainless steel hot-roll annealing steel plate, is according to any one of claims 1 to 3 The manufacturing method of ferrite-group stainless steel hot-roll annealing steel plate, which is characterized in that
In the hot-rolled process of finish rolling for carrying out three passages or more, the temperature range of final three passages of finish rolling is set as 800~1100 DEG C and the accumulation reduction ratio of final three passages is set as 25% or more and obtains hot rolled steel plate,
Hot rolled plate annealing is further carried out at 800~1100 DEG C to the hot rolled steel plate.
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